Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior

Posts

1,411

Post Likes

Likes (Given)

0

Likes (Received)

0

Dislikes (Given)

0

Dislikes (Received)

0

Originally Posted by dan sw fl

If you continue to try to work with "this HVAC idiot",
you get what The Owner deserves.
if the root cause - windows - is not addressed,
you get what you get
and don't have a fit.

Not a very productive response, Designer Dan. I suppose that you are suggesting that I replace 70'+ of Southern exposure windows or maybe installing $1,000's of film on the windows that kill the beautiful view and may or may not fix the sun load. The true "idiot" in this situation is the original designer that I never met. Placing only one HVAC system in this fairly large, walk-out house and then enclosing all of the duct work in dry wall to prevent any cost-effective duct solutions and then placing the tsat in probably the hottest room in the house. Your smart reply reflects no content that I, a quite accomplished designer in another environment, would attribute to an effective designer. Maybe it's just that it's early and you have a bad day in front of you or, if not, you could just skip reading the posts on this thread.

Now back to Beenthere's comment. Installing additional sensors is a matter of what's cost-effective. This house is fairly large, built in 1994, and each sensor requires a wall penetration and hopefully finding a reasonable wiring path back to the tsat digital control in the garage. The two locations that I think will work are above the return in the highly-used, partially buried, lower level that is naturally cooler and the other is in the first floor master bedroom near the wall vent penetration for when the door is closed and which is away from the hottest room. One sensor is an easy install and the other not so much. These two locations are much more reflective of the true temperature of the rest of the house. During the heating season, the average of these two temperatures will be lower than in the hot room and should cause longer run times to reach the tsat setting. The longer run times should also simulate running just the fan for the hot room causing the air handler to mix the hot air from that room and possibly lowering it there without all of that blowing cool air throughout the house with just the fan. In addition, my HVAC pro feels that too many sensors will solve the problem in no specific location which I kind of agree with as long as the selected locations are indicative of the true house temperature.

So, Beenthere, given that we select appropriate senor locations, do you agree that the proposed two-sensor scenario using the average of the tsat and the new sensor location using the tsat 340 setting is at least technically feasible without any undocumented workarounds for Honeywell's tsat/sensor scenarios?

Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior

Posts

1,411

Post Likes

Likes (Given)

0

Likes (Received)

0

Dislikes (Given)

0

Dislikes (Received)

0

Originally Posted by beenthere

Nope. Need two sensors, and the stat is not one of them.

Not any harder to install 2 sensors. Then to install one sensor and move the thermostat to another location.

Beenthere, I have read some technical documentation in my day but I am totally confused by the cross statements between the Honeywell YTH9421C1002/U tsat and the C7189U1005 indoor sensor. The tsat doc says for the 340 setting that you can display average of two indoor temperature sensors and indeed that The temperature sensor in the thermostat is disabled when using remote indoor temperature sensor(s):

Indoor temperature sensors will display the temperature at the sensor location or an average of two indoor temperature sensors, not including the thermostat. The temperature sensor in the thermostat is disabled when using temperature sensor in remote indoor temperature sensor(s).

Then the C7189U1005 indoor sensor doc shows figures on page 3 of legal configurations for 1, 4 and 9 sensors and NOT 2.

- First, why would one even want to "display" the tsat temperature in an average if it is "disabled" by adding an indoor sensor?

- The tsat 340 setting talks about displaying the "average of two indoor temperature sensors" which is an illegal, configuration????

- Beenthere says that it is "Not any harder to install 2 sensors" which is an illegal Honeywell configuration????

- Beenthere said in the past that there is an "undocumented work around" for two indoor sensors but I can't find any documentation to provide my HVAC pro.???

- Is it just time for me to say forget it, because I cannot resolve the communication path between Honeywell/this forum/my HVAC pro??? I have no idea what to order for him nor does he and has little interest in researching it.

The close-to-the-vest format on this forum is just pure frustration for a home owner trying to solve a real HVAC problem. I appreciate the concern over do-it-youselfers but I am NOT one and it would be a cold day in .... before I start running wire in my house. The change in focus of this forum a while back is hard for a home owner to navigate.

PS: thank you, catmanacman, for the suggestion, but it sounds like I would have to scrap all of my tsat equipment and start over to do wireless.

No idea why anyone would want to display an average temp but not use it to control temp.
Averaging of one remote and the stat is useless.
Its not an "illegal" configuration. Honeywell the support that you talked to is residential, not commercial, so they probably don't even know they make the 20,000 ohm sensors.
Thats up to you. To me its simple. Get the 20,000 ohm sensors and install them.

The install manuals are not written by engineers. They are written by people that went to school to learn how to write technical documents. They don't really know how whatever they are writting about works. they just transcribe notes on operation from the engineers. And those notes aren't always clear, so the writer will sometimes adlib it.

Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior

Posts

1,411

Post Likes

Likes (Given)

0

Likes (Received)

0

Dislikes (Given)

0

Dislikes (Received)

0

Originally Posted by beenthere

No idea why anyone would want to display an average temp but not use it to control temp.
Averaging of one remote and the stat is useless.
Its not an "illegal" configuration. Honeywell the support that you talked to is residential, not commercial, so they probably don't even know they make the 20,000 ohm sensors.
Thats up to you. To me its simple. Get the 20,000 ohm sensors and install them.

The install manuals are not written by engineers. They are written by people that went to school to learn how to write technical documents. They don't really know how whatever they are writting about works. they just transcribe notes on operation from the engineers. And those notes aren't always clear, so the writer will sometimes adlib it.

Beenthere, I think this is getting through my HVAC thick skull. I have been proceeding along assuming that you were recommending that a very specific 20,000 ohm electrical component was needed along with 2 Honeywell C7189U1005 indoor sensors and that they are to be wired in some undocumented electrical circuit which I couldn't understand why you couldn't describe that circuit for my HVAC pro. I finally located the TR21 wall mounted sensor assembly and think I know what you really meant. Please verify this scenario:

Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior

Posts

1,411

Post Likes

Likes (Given)

0

Likes (Received)

0

Dislikes (Given)

0

Dislikes (Received)

0

We have had the two 20k remote temperature sensors installed for a cooling and big part of heating season. I was a bit disturbed when the installers didn't seem to know that these two sensors needed to be hooked up in parallel versus serial in order to get an effective 10k circuit. Whereas I know little to nothing about how to wire real-world circuits, I waded in based on circuit theory and insisted that they needed to wire them in this way. Now I am trying to figure out why temps in the three locations and the furnace tstat seem to disagree. I would appreciate any guidance that seems needed.

We set the tstat at 69 during the day. I note that three thermometers in different locations, two close or in the same room as a sensor, do not agree with this setting. Most of the time the temps measured are 2 or more degrees higher than that registered on the tstat. As I understand, if wired and set correctly, the tstat should show the average temp for the two sensors. I also understand from the literature that the sensors may vary up to 1 1/2 degrees. I also understand that the proximity of a vent could effect these readings.

When I mentally average the measured temperatures at the two sensors, it seems never to agree with the tstat "averaged" temperature. Can you verify that should these sensors have been wired incorrectly, in series say, that the tstat would be way off due to an effective 20k circuit when it is calibrated to a 10k circuit? Also, does the temperature variances between three locations and the averaged tstat temperature sound good enough?